Question

Can I cast a pointer to a double as type char *, then use that pointer to break the double into bytes?

Here’s example code:

double data;
double *dblPoint = &data;
unsigned char *bytePoint = (unsigned char *)dblPoint;
unsigned char byteArray[sizeof (double)];
unsigned int i;

for(i = 0; i < sizeof(double); i++) {
    byteArray[i] = *(bytePoint + i);
}

byteArray is then transmitted via UART to another computer and reconstructed (bytesReceived contains the incoming data):

unsigned char bytesReceived[sizeof (double)];

double reconstData;
double *newDblPoint;
unsigned int i;

newDblPoint = bytesReceived;
reconstData = *dblPoint;

So, after all that, would data == reconstData?

Answer 1

Your first example can be simplified to:

double data;
unsigned char bytesReceived[sizeof double];
memcpy ( bytesReceived, &data, sizeof data);

Your second example is not valid: the buffer

unsigned char bytesReceived[sizeof double];

Is not necessarily aligned on a “double” boundary, so that the cast

newDblPoint = bytesReceived;
reconstData = *dblPoint;

will attempt to dereference an unaligned pointer.